Exciter assemblies

ABSTRACT

Provided herein are systems, devices, assemblies, and methods for generating exciter signals, for example, to activate a remotely located tag. The systems, devices, assemblies, and methods find use in a variety of application including medical applications for the locating of a tag in a subject.

The present application is a continuation of U.S. patent applicationSer. No. 16/001,552, filed Jun. 6, 2018, now allowed, which claimspriority to U.S. Provisional Application Ser. No. 62/680,750 filed Jun.5, 2018, each of which is herein incorporated by reference in itsentirety.

FIELD

Provided herein are systems, devices, assemblies, and methods forgenerating exciter signals, for example, to activate a remotely locatedmarker tag. The systems, devices, assemblies, and methods find use in avariety of applications including medical applications for the locatingof a tag in a subject.

BACKGROUND

A common and serious challenge for many medical procedures is theaccurate localization of treatment areas. For example, the location oflesions, such as tumors that are to undergo treatment, includingsurgical resection, continues to present a challenge to the medicalcommunity. Existing systems are expensive, complex, time-consuming, andoften unpleasant for the patient. Such issues are illustrated by thesurgical treatment of breast lesions. A common technique used in breasttumor surgery is wire localization of the lesions.

Precise preoperative localization of some breast lesions is necessarybefore removal of the lesion. Wire localization is used to mark thelocation of a breast abnormality. The procedure ensures greater accuracyfor a breast biopsy or lumpectomy. The surgeon typically uses the wireas a guide to the tissue that needs to be removed. Wire localization istypically conducted in the radiology department of the hospital orsurgical center. Mammograms (or in some cases, ultrasound images) aretaken to show the location of the breast abnormality. Patients are awakeduring the placement of the wire, but the breast tissue is numbed toreduce or avoid pain from the needle or the wire. It is possible to feelpressure or pulling sensations during the wire placement. Once imageshave been taken, and the tissue has been numbed, the radiologist willuse a needle to target the breast abnormality. The tip of this needlerests in the location that the surgeon needs to find in order to removethe right tissue. A slender wire is threaded down through the needle andout of its tip, to lodge at the target tissue. The needle is removed,leaving the wire in place. With the wire in place, the patient hasanother mammogram, to check that the tip of the wire is properlypositioned. If the wire is not in the correct place, the radiologistwill reposition and re-check it, to ensure accurate placement. When thewire is finally positioned, it will be secured in place with tape or abandage. The wire localization procedure can take about an hour, and isusually scheduled hours before biopsy or lumpectomy. Thus, the patientmust often wait hours for surgery with the wire present in their bodyand protruding from their skin. The wire is removed, along with somebreast tissue, during surgery. This process takes many hours, involvesmultiple imaging steps, and is inconvenient and unpleasant for thepatient—as well as being expensive.

A similar type of procedure is done to localize pulmonary nodules priorto resection. In some cases where pulmonary nodules may be difficult tolocate at conventional open surgery or at thoracoscopy, a hook wire,injection of visible dye, or a radionuclide is placed in or around thenodule in an attempt to improve localization prior to removal. Thisprocedure usually takes place in the computerized tomography (CT) suiteprior to the removal of the nodule. The patient is then transported tothe surgical unit and the surgeon cuts down on the wire, uses aradionuclide detector, or uses visual landmarks to localize and removethe nodule.

In other types of surgeries and medical procedures, physicians may havetrouble locating a target prior to removal or manipulation. Examples ofthis include the removal of masses, fluid collections, foreign bodies ordiseased tissues. Other times, placements of catheters or otherpercutaneous procedures are performed either without directvisualization or with the lack of a specific guidance modality.Performing procedures without precise guidance can increase the amountof damage to normal tissues and decrease the patient's functionalstatus.

Percutaneous biopsy is a well-accepted, safe procedure performed invirtually every hospital. Biopsy often entails placement of a co-axialguide needle through which the biopsy device is placed into the target.Many of the lesions that are removed, punctured or manipulated asdescribed above have previously undergone successful percutaneousbiopsy. The placement of the guide needle for biopsy is an opportunityto place a fiduciary or other localizing system without causingadditional tissue trauma than the patient would otherwise undergo.

Many other medical devices and procedures could benefit from improvedtissue localization. These include any procedure or test that isdegraded by any bodily motion such as cardiac motion, respiratorymotion, motion produced by the musculoskeletal system, orgastrointestinal/genitourinary motion. Examples of these includeexternal beam radiation therapy, placement of brachytherapy seeds,imaging tests including but not limited to CT, MRI, fluoroscopy,ultrasound, and nuclear medicine, biopsies performed in any fashion,endoscopy, laparoscopic and thoracoscopic surgery and open surgicalprocedures.

Improved systems and methods are needed for tissue localization formedical procedures.

SUMMARY

Provided herein are systems, devices, assemblies, and methods forgenerating exciter signals, for example, to activate a remotely locatedtag. The systems, devices, assemblies, and methods find use in a varietyof applications including medical applications for the locating of a tagin a subject. While the description below illustrates the inventionusing examples of human surgical procedures, it should be appreciatedthat the invention is not so limited and includes veterinaryapplications, agricultural applications, industrial applications,mechanical applications, military applications (e.g., sensing andremoval of dangerous materials from an object or region), aerospaceapplications, and the like.

In some embodiments, provided herein are systems comprising one or moreor each of: a) one or more tags; b) a remote activation device (e.g.,exciter assembly) that generates a magnetic field (e.g., time varyingmagnetic field) within a region of the tag, the remote activating devicecomprising four or more exciter coils each configured to flow current ineither a clockwise or counterclockwise direction such that the magneticfield generated by the remote activating device may be selectivelygenerated in substantially any of X, Y, or Z directions (e.g., to ensurethat the tag(s) can be excited for any angle that it may be placed); andc) a plurality of sensors configured to detect a signal from the one ormore tags when the one or more tags is exposed to the magnetic field. Insome embodiments, the four or more exciter coils are connected inseries.

In some embodiments, four of the exciter coils are in a layout of tworows centered at coordinates (X1, Y1), (X1, Y2), (X2, Y1), and (X2, Y2).In some embodiments, the remote activating device (e.g., exciterassembly) comprises three current flow configurations: a) all currentclockwise to simulate an exciter coil aligned with a direction normal tothe Z axis; b) exciter coils centered at (X2, Y1), (X2, Y2) runningcurrent counter-clockwise to simulate an exciter coil aligned to the Xaxis; and c) exciter coils centered at (X1, Y2), (X2, Y2) runningcurrent counter-clockwise to simulate an exciter coil alignedsubstantially to the Y axis. In some embodiments, the remote activatingdevice (e.g., exciter assembly) comprises a plurality of relays thatprovide a switching function to accomplish the current direction change(polarity) yet maintain an excitation frequency by switching additionalcapacitive reactance. In some embodiments, the switching functioninserts additional series capacitive reactance via a capacitance elementwhen total inductance is increased so that a tuning center frequency ismaintained at said excitation frequency (e.g., the total inductance ofthe 4 coils, when 4 coils are employed, varies as the current directionis changed within each coil or coil pair). In some embodiments, thecapacitance element is comprised of multiple capacitors (e.g., to betteraccommodate the voltage potential at resonance and/or to provide greaterflexibility on frequency tuning). In some embodiments, the remoteactivating device further comprises a balun in proximity to the excitercoils. The balun eliminates common mode current that would otherwiseproduce unwanted electric field components that could otherwise reduceaccuracy. It also provides impedance transformation to match the realcomponent of the coil impedance to that of the transmission line,typically 50 Ohms. In some embodiments, the balun has eight turns on aprimary side (amplifier side) and four turns on a secondary side (coilside). In some embodiments, the system further comprises an amplifier inelectronic communication with the remote activating device. In someembodiments, the system further comprises a computer that controlsmagnetic field generation and sensor detection. In some embodiments, thecomputer comprises a hunting algorithm (e.g., embodied in softwarerunning on the processor) that adjusts the magnetic field orientation toidentify (and power) optimal detection of one or more tags.

Also provided herein are uses of any of the above systems (e.g., fordetecting a position of a tag in an object; for detecting a position ofa tag relative to a medical device; etc.).

Further provided herein are methods of identifying a position of a tag,comprising: a) providing any of the systems described herein; b) placingthe tag in an object; c) generating a magnetic field with the activatingdevice; and d) identifying a position of said tag in said object bycollecting information emitted from the tag with the witness stations.In some embodiments, the position or comprises relative location ordistance of the tag to a medical device.

In certain embodiments, provided herein are systems and devicescomprising: an exciter assembly that cycles between generating at leastfirst, second, and third magnetic fields (e.g., first, second, third,fourth, fifth, sixth, seventh, and/or eighth magnetic fields) forcausing a tag to generate a signal, wherein the exciter assemblycomprises A) a base substrate, B) a first exciter coil attached to thebase substrate, wherein current in the first exciter coil travelsclockwise when the first, second, and third magnetic fields aregenerated, C) a second exciter coil attached to base substrate, whereincurrent in the second exciter coil travels clockwise when the first andsecond magnetic fields are generated, and travels counterclockwise whenthe third magnetic field is generated, D) a third exciter coil attachedto the base substrate, wherein current in the third exciter coil travelsclockwise when the first and third magnetic fields are generated, andtravels counterclockwise when the second magnetic field is generated;and E) a fourth exciter attached to the base substrate, wherein currentin the fourth exciter coil travels clockwise when the first magneticfields is generated, and travels counterclockwise when the second andthird magnetic fields are generated.

Exciter coils, for example, may be wound using Litz wire to minimizeresistive losses due to the skin effect that occurs as frequencyincreases. The number of turns is generally chosen to maximize coil “Q”(the ratio of inductance/resistance). An exemplary coil example is 63turns of Litz wire comprised of 100 strands of 38 AWG wire. Inductanceof an individual coil measures about 1.1 mH and Q (ratio of inductivereactance to resistance) measures over 500 at 134.5 KHz. Other coilconstructions using other wire with different values of inductance and Qmay be used. However, it is generally desired to keep “Q” as high aspossible to minimize resistive losses that result in loss of efficiencyand greater thermal heating.

In some embodiments, provided herein are systems and devices comprising:a) a base substrate, b) first, second, third, and fourth exciter coilsattached to the substrate and configured to generate a magnetic fieldfor causing a tag to generate a signal, c) a balun circuit electricallylinked to the first, second, third, and fourth exciter coils.

In particular embodiments, each of the second, third, and fourth excitercoils are operatively connected to a switch that controls the directionof current through a coil. In certain embodiments, each switch comprisesa relay element, a PIN diode, a Field Effect Transistor, or other solidstate switching device. In particular embodiments, each switchadditionally switches at least one capacitor (e.g., two capacitors) intothe circuit to keep the resonant frequency of the series combination ofexciter coils constant regardless of the change in overall coilinductance that results from changing coil polarity.

The inductance of an exemplary exciter coil system measures 1.1 mH withQ>500 for each individual coil. The inductance of the series combinationof 4 coils (e.g., as shown in FIG. 4A) varies with polarity (currentdirection) of the coils because of the interaction of the magnetic fluxproduced by each coil. The inductance of the series combination of all 4exemplary coils measures 3.9 mH with Q=435 for the current directiondepicted in FIG. 5 where all coils have current flowing in the clockwisedirection. The inductance of the series combination of all 4 exemplarycoils measures 4.6 mH with Q=500 for the current direction depicted inFIG. 6 where coils A and B have current in the clockwise direction andcoils C and D have current flowing in the counterclockwise direction.The inductance of the series combination of all 4 exemplary coilsmeasures 4.3 mH with Q=473 for the current direction depicted in FIG. 7where coils A and C have current in the clockwise direction and coils Band D have current flowing in the counterclockwise direction. Thisvariation in total inductance necessitates switching in appropriatecompensation capacitors when the coil polarity is changed.

In some embodiments, the components of the relay or switch andassociated capacitors may be placed on a ceramic substrate to providesecure mounting, excellent dielectric properties, and also serve as aheat spreader to reduce localized heating of individual components.

In some embodiments, the systems and devices further comprise: aplurality of witness coils or witness station assemblies attached to thesubstrate and configured to detect the signal from the tag. In someembodiments, the witness coils are placed such that the axis of the coilis co-planar with the central plane of the exciter coils. In this plane,the magnetic flux produced by the exciter is orthogonal to the sensingaxis of the witness coils for every combination of coil currentdirection described previously. The orthogonal exciter current does notinduce a signal into the witness coils and thus provides isolationbetween the exciter coil and witness coils. This isolation is generallyneeded to achieve the needed system dynamic range so that the very weaktag signal may be detected in the presence of the very large excitermagnetic field. This isolation is also important because crosstalkbetween the exciter coil and witness coils would otherwise greatlyimpede navigation because the crosstalk term would contributesignificant signal arising from the same magnetic dipole (the exciter)to all witness coils and therefore the witness coils would lose theirspatial independence. An additional point is that the presence of thez-oriented exciter significantly distorts the z-component of the tag(and emitter) magnetic field, making it less useful for navigation.

In further embodiments, the plurality of witness coils, or plurality ofwitness station assemblies, comprises six to thirty witness coils (e.g.,6 . . . 9 . . . 12 . . . 20 . . . or 30). In additional embodiments, theplurality of witness coils: i) are located on opposing sides of saidbase substrate, but not adjacent to said opposing sides, and/or ii) areeach positioned to alternate opposite orientation along x and y axeswith respect to other witness coils. This positioning minimizescrosstalk between witness coils and thereby reduces the degree thatcrosstalk compensation that is applied (e.g., by a mathematic solversoftware).

In some embodiments, the systems and devices further comprise aplurality of printed circuit boards, wherein each of the plurality ofwitness coils is operably linked to one of the plurality of circuitboards. In certain embodiments, each circuit board comprises at leasttwo capacitors and at least one balun circuit. In particularembodiments, the systems and devices further comprise the tag.

In certain embodiments, the systems and devices further comprise a baluncircuit that is electrically linked to the first, second, third, andfourth exciter coils. In further embodiments, the systems and devicesfurther comprise a cable bundle that is electrically linked to the baluncircuit. In additional embodiments, the systems and devices furthercomprise a plurality of witness coils attached to the substrate andconfigured to detect the signal from the tag, wherein the plurality ofwitness coils are electrically linked to the cable bundle.

In some embodiments, the systems and devices further comprise at leastone self-test emitter. In other embodiments, the systems and methodsfurther comprise a top cover, wherein the top cover mates with the basesubstrate to enclose the first, second, third, and fourth exciter coilstherein.

In other embodiments, the systems and devices further comprise a systemelectronics enclosure which is configured to provide a signal to thefirst, second, third, and fourth exciter coils. In other embodiments,the center of each of the first, second, third, and fourth exciter coilsis separated from each other by at least 5 centimeters (e.g., 5 . . . 10. . . 15 . . . 25 . . . 100 . . . 1000 cm). In other embodiments, thecenter of each of the first, second, third, and fourth exciter coils isseparated from each other by 2-5 times the largest dimension of thecoils themselves. In certain embodiments, the fourth exciter coil ispositioned next to the second exciter coil, and wherein the thirdexciter coil is positioned next to the first exciter coil and diagonalfrom the second exciter coil.

In some embodiments, provided herein are methods comprising: a)positioning the systems or devices disclosed herein below or near apatient that has a tag located therein, and b) activating the system ordevice such that an magnetic field is generated, thereby causing the tagto generate a signal.

In some embodiments, provided herein are systems and devices comprisinga witness station assembly, wherein the witness station assemblycomprises: a) a witness coil, wherein the witness coil comprises: i) ametal core having a coil-free proximal end, a coil-free distal end, anda central region, and ii) coil windings wound around the central regionof the metal core, b) first and second witness coil brackets, and c)first and second elastomeric parts, wherein the coil-free proximal endof the metal core is secured between the first witness coil bracket andthe first elastomeric part, and wherein the coil-free distal end of themetal core is secured between the second witness coil bracket and thesecond elastomeric part. In certain embodiments the systems or devicesfurther comprise a remote activation device (e.g., as described herein),wherein the remote activation device comprises at least one excitercoil. In further embodiments, the systems and devices further comprise:an exciter assembly (e.g., as described herein), wherein the exciterassembly comprises at least one exciter coil.

In further embodiments, the first and second witness coil brackets eachcomprises at least one adjustment part (e.g., two adjustment screws). Insome embodiments, the at least one adjustment part comprises at leastone screw and/or at least one rod. In other embodiments, the witnessstation assembly further comprises an electronics part electricallylinked to the witness coil. In other embodiments, the electronics partcomprises at least one capacitor and/or at least one balun circuit. Infurther embodiments, the electronics part comprises a printed circuitboard.

In certain embodiments, the witness station assembly further comprises afaraday shield. In other embodiments, the witness station assemblyfurther comprises: i) an electronics part electrically linked to saidwitness coil, and ii) a faraday shield. In additional embodiments, thefirst and second elastomeric parts comprise a material selected from: anelastomer polymer and a spring.

In some embodiments, the metal core comprise a ferrite core. In otherembodiments, the metal core has a diameter of 4 to 25 mm (4 . . . 8 . .. 12 . . . 14 . . . 16 . . . 25 mm). In certain embodiments, the metalcore has a length of 15 to 75 mm (e.g., 15 . . . 30 . . . 45 . . . 58 .. . 75 mm). In particular embodiments, the coil windings comprise metalwire. In other embodiments, the metal wire is wound around said metalcore 150-300 times. In further embodiments, the first and second witnesscoil brackets each comprises a notch configured to fit the wire-freeproximal end and/or the wire-free distal end of said metal core.

In particular embodiments, provided herein are devices and systemscomprising: a) an attachment component (e.g., a sheath) configured to beattached to a hand-held medical device with a device tip, wherein theattachment component comprises: i) a proximal end, ii) an angled distalend, wherein the angled distal end comprises a distal end openingconfigured to allow the device tip, but not the remainder of the medicaldevice, to pass therethrough, and iii) a main body stretching betweenthe proximal end and the angled distal end, and b) first and secondlocation emitters attached to the attachment component.

In certain embodiments, the angled distal end has an angle of at least35 degrees with respect to the longitudinal axis of the attachmentcomponent (e.g., at least 35 . . . 45 . . . 65 . . . 85 . . . or 95degrees). In some embodiments, the angled distal end has an angle ofabout 90 degrees with respect to the longitudinal axis of the attachmentcomponent. In further embodiments, the first and second locationemitters are attached to the main body of the attachment component(e.g., spaced apart).

In other embodiments, systems and devices further comprise: c) a displaycomponent housing, wherein the display component housing is attached to,or attachable to, the proximal end of the attachment component. Inadditional embodiments, the systems and devices further comprise adisplay component attached to the display component housing, wherein thedisplay component comprises a display screen (e.g., LCD screen) fordisplaying the location of an implanted tag in a patient relative to thedevice tip on a medical device. In other embodiments, the displaycomponent housing comprises a cable management component. In additionalembodiments, the display component housing comprises a housing taperedconnection. In further embodiments, the proximal end of the attachmentcomponent comprises a proximal tapered connection.

In other embodiments, the devices and systems further comprise first andsecond location emitter wire leads, wherein the first location emitterwire lead is electrically linked to the first location emitter (e.g.,small coil), and the second location emitter wire lead is electricallylinked to the second location emitter (e.g., small coil). In otherembodiments, the systems and devices further comprise: c) an adhesivestrip sized and shaped to cover at least 50% (e.g., 50% . . . 75% . . .90%) of the attachment component main body, and configured to adhere theattachment component to the medical device. In certain embodiments, thesystems and devices further comprise: c) the medical device. In otherembodiments, the medical device comprises an electro-cautery surgicaldevice.

Definitions

As used herein, the terms “processor” and “central processing unit” or“CPU” are used interchangeably and refer to a device that is able toread a program from a computer memory (e.g., ROM or other computermemory) and perform a set of steps according to the program.

As used herein, the terms “computer memory” and “computer memory device”refer to any storage media readable by a computer processor. Examples ofcomputer memory include, but are not limited to, RAM, ROM, computerchips, digital video discs (DVD), compact discs (CDs), hard disk drives(HDD), optical discs, and magnetic tape. In certain embodiments, thecomputer memory and computer processor are part of a non-transitorycomputer (e.g., in the control unit). In certain embodiments,non-transitory computer readable media is employed, where non-transitorycomputer-readable media comprises all computer-readable media with thesole exception being a transitory, propagating signal.

As used herein, the term “computer readable medium” refers to any deviceor system for storing and providing information (e.g., data andinstructions) to a computer processor. Examples of computer readablemedia include, but are not limited to, DVDs, CDs, hard disk drives,magnetic tape and servers for streaming media over networks, whetherlocal or distant (e.g., cloud-based).

As used herein, the term “in electronic communication” refers toelectrical devices (e.g., computers, processors, etc.) that areconfigured to communicate with one another through direct or indirectsignaling. Likewise, a computer configured to transmit (e.g., throughcables, wires, infrared signals, telephone lines, airwaves, etc.)information to another computer or device, is in electroniccommunication with the other computer or device.

As used herein, the term “transmitting” refers to the movement ofinformation (e.g., data) from one location to another (e.g., from onedevice to another) using any suitable means.

As used herein, the term “subject” or “patient” refers to any animal(e.g., a mammal), including, but not limited to, humans, non-humanprimates, companion animals, livestock, equines, rodents, and the like,which is to be the recipient of a particular treatment. Typically, theterms “subject” and “patient” are used interchangeably herein inreference to a human subject.

As used herein, the term “subject/patient suspected of having cancer”refers to a subject that presents one or more symptoms indicative of acancer (e.g., a noticeable lump or mass) or is being screened for acancer (e.g., during a routine physical). A subject suspected of havingcancer may also have one or more risk factors. A subject suspected ofhaving cancer has generally not been tested for cancer. However, a“subject suspected of having cancer” encompasses an individual who hasreceived an initial diagnosis (e.g., a CT scan showing a mass) but forwhom the stage of cancer is not known. The term further includes peoplewho once had cancer (e.g., an individual in remission).

As used herein, the term “biopsy tissue” refers to a sample of tissue(e.g., breast tissue) that is removed from a subject for the purpose ofdetermining if the sample contains cancerous tissue. In someembodiments, biopsy tissue is obtained because a subject is suspected ofhaving cancer. The biopsy tissue is then examined (e.g., by microscopy;by molecular testing) for the presence or absence of cancer.

As used herein, the term “sample” is used in its broadest sense. In onesense, it is meant to include a specimen or culture obtained from anysource, as well as biological and environmental samples. Biologicalsamples may be obtained from animals (including humans) and encompassfluids, solids, tissues, and gases. Biological samples include tissue,blood products, such as plasma, serum and the like. Such examples arenot however to be construed as limiting the sample types applicable tothe present invention.

As used herein, the term “tag” or “marker tag” refers to the smallimplantable marker that, when excited by an exciter's time varyingmagnetic field, will emit a “homing beacon” spectrum of frequency(ies)received by the witness coil(s) and used to determine its location. Itmay be programmed to produce a unique spectrum, thus permitting multipletags to be implanted and located simultaneously.

DESCRIPTION OF DRAWINGS

FIG. 1 shows an exemplary positioning of an exciter assembly, a medicaldevice with display component attached, and a patient with a tagimplanted next to a tumor.

FIG. 2 shows an attachment component 10 that is attached to a medicaldevice 20, which has a device tip 25. The attachment component 10 hastwo location emitters 70 located therein. The attachment component 10 isattached to, or integral, with a display component 40.

FIG. 3 shows an exemplary coil configuration of an exciter assembly.

FIG. 4A shows an exemplary exciter assembly 250 attached to controller210 via a cable bundle 200.

FIG. 4B shows an exemplary witness coil assembly (aka witness stationassembly) 161.

FIG. 4C shows an exemplary witness coil 160, including the threedirections in which wire is wound to form coils 167 over the metal core166.

FIG. 5 shows an exemplary exciter assembly with four exciter coils(Coils A-D), where the current is flowing in the clockwise direction inall four exciter coils.

FIG. 6 shows an exemplary exciter assembly with four exciter coils(Coils A-D), where the current is flowing in the clockwise direction inCoils A and B, and flowing in the counterclockwise direction in Coils Cand D.

FIG. 7 shows an exemplary exciter assembly with four exciter coils(Coils A-D), where the current is flowing in the clockwise direction inCoils A and C, and flowing in the counterclockwise direction in Coils Band D.

FIG. 8 shows an exemplary exciter assembly 250 with the top cover 230on. The exciter assembly 250 is shown with cable bundle 200 leadingtherein.

FIG. 9 shows an exemplary attachment component 10, with an angled distalend 300 that the distal tip 25 of the medical device 20 is insertedthrough.

FIG. 10. Panel A shows the distal end 25 of a medical device 20 after itis initially inserted through the angled distal end 300 of attachmentcomponent 10. Panel B shows attachment component wire 60 prior to beingattached to the cable management component 315 of the display componenthousing 330. Panel B shows attachment component wire 60 prior to beingattached to the cable management component 315 of the display componenthousing 330. Panel B also shows the housing tapered connection 340 thatthe proximal end tapered connection 350 of the attachment component 10is inserted into. The cable management component 315 has two clips thatattached to and align both the attachment component wire 60 and themedical device wire 50.

FIG. 11 shows an exemplary attachment component 10 attached to a displaycomponent housing 330. The attachment component 10 has a pair oflocation emitters 70, which are linked to location emitter wires leads72 which are inside tube 360. The attachment component also has anangled distal end 300 with a distal end opening 305, which allows thetip of a surgical or other device to be inserted therethrough. Thedisplay component housing 330 has a cable management component 315,composed of a pair of clips for holding insulated wires.

FIG. 12 shows an exemplary attachment component 10 attached to a displaycomponent housing 330 with a display component 40 located therein. Adisplay cover 370 is shown, which is used to secure the displaycomponent 40 inside the display component housing 330. Also shown is anadhesive strip 380, which is shaped and sized to fit inside theattachment component and help secure a medical device to the attachmentcomponent.

FIG. 13. Panel A shows the proximal end tapered connection 350 of theattachment component 10, which is configured to push-fit into housingtapered connection 340 of the display component housing 330. Panel Bshows a close up of section A of Panel A, including cable managementtapered connection 317 that is part of cable management component 315and designed to be inserted into tapered connection hole 319 of displaycomponent housing 330. Cable management tapered connection 317 includesa flat part 318 to lock angular position.

FIG. 14 shows an exemplary system for localizing a tag that is implantedin a patient. The system is composed of an exciter assembly that emitssignals that activate the tag(s) in the patient. A systems electronicsenclosure is shown as a mobile cart, which delivers signals to theexciter assembly and receives and processes signals from the tag(s) inthe patient. Guidance for a surgeon is displayed on the displaycomponent, as well as on a screen on the systems electronics enclosure.

DETAILED DESCRIPTION

Provided herein are systems, devices, assemblies, and methods forgenerating exciter signals, for example, to activate a remotely locatedtag. The systems, devices, assemblies, and methods find use in a varietyof application including medical applications for the locating of a tagin a subject. While the specification focuses on medical uses in humantissues, it should be understood that the systems and methods findbroader use, including non-human uses (e.g., use with non-human animalssuch as livestock, companion animals, wild animals, or any veterinarysettings). For example, the system may be used in environmentalsettings, agricultural settings, industrial settings, or the like.

A. Addressing Variable Alignment of an External Coil (e.g., Tag Coil)with the Exciter Assembly

In some embodiments, the exciter is configured to provide power to atag, independent of the alignment of the coil of the tag with theexciter. For example, in some embodiments, power transfer to a tag maybe dependent on the relative orientation of the exciter magnetic fieldto the tag. In some such embodiments, absent a corrective measure, thetag may only collect power from the portion of field aligned to thetag's coil (e.g., a ferrite-core coil contained in the tag). This issuecould be resolved by including multiple exciters capable of producingall three orthogonal directions of the magnetic field. This, however,leads to a thicker assembly and prevents both rejection of primaryexciter coil (e.g., located in the exciter assembly) to sensing coilcoupling (also located in the exciter assembly) (see section B below)and rejection of secondary field coupling between the tags/emitters andexciter coil that subsequently couple to the sensing coils and impairlocalization of the tags or emitters (see section C below). To addressthis challenge, provided herein are configurations of the exciterassembly that provide a mechanism of changing the orientation of themagnetic field with exciter coils that can be deployed in only onemagnetic direction.

In some embodiments, this is accomplished by having multiple coils inthe exciter assembly (see, e.g., FIG. 4A), and setting the direction ofcurrent within each coil to either clockwise or counterclockwise (see,e.g., FIGS. 5-7). In some embodiments, the coils are connected in seriesso that the same current is running in each. In some embodiments, a coillayout comprises four coils in two rows, centered at (X1, Y1), (X1, Y2),(X2, Y1), and (X2, Y2) coordinates with three sets of current flowconfigurations: Configuration 1: all current clockwise to simulate anexciter coil aligned with its plane normal to the Z axis; Configuration2: coils centered at (X2, Y1), (X2, Y2) running currentcounter-clockwise to simulate an exciter coil aligned to the X axis; andConfiguration 3: coils centered at (X1, Y2), (X2, Y2) running currentcounter-clockwise to simulate an exciter coil aligned to the Y axis. Anynumber of other coil configurations may be employed. For efficiency, itis desired (although not required) to minimize the number of componentsand overall complexity of the design. However, in some embodiments, itmay be desirable to have more than four coils (e.g., 6, 8, 10, 16, etc.)in the exciter assembly to provide more flexibility for changing fielddirectionality, albeit at the expense of system complexity.

Tuning of the coils in the exciter assembly for each configurationrequires less change between configurations when the same current isflowing through all the coils in every configuration. This is becausethe effect of one exciter coil on the others is dependent on the stateof the first exciter coil (open circuit, current-carrying, etc.).

To provide optimal performance, the area of the exciter coils should bemaximized, and the distance between the centers of the coils should bemaximized. A larger area coil provides a higher field for the sameapplied current. Coils separated by larger distances provide a largerdirectional change for Configurations 2 and 3.

FIG. 3 provides an exemplary schematic of a four coil exciter assemblyin some embodiments of the invention, with the four coils labeled CoilA, Coil B, Coil C, and Coil D (see FIG. 4A).

For medical uses, where the exciter assembly is provided in a flatplanar mode (e.g., pad) beneath a patient, a clinically preferred systemgeometry entails that all four coils are placed very close to eachother. As a result, the magnetic coupling between each coil varies withindividual coil polarity and therefore the total inductance of all fourcoils in series varies with coil polarity combinations. Thus, optimalperformance will necessarily balance competing factors. To compensatefor this, in some embodiments, a system of switching is employed inwhich additional series capacitive reactance is inserted when the totalinductance is increased so that the tuning center frequency ismaintained at the desired excitation frequency. In a preferredembodiment shown in FIG. 3, relays are utilized for switching. Otherembodiments may employ solid state switching approaches such as PINdiodes. Any suitable mechanism that achieves the switching may beemployed.

In some embodiments, the centers of the coils are separated by 10 . . .50 . . . 100 . . . 500 . . . or 1000 cm. In some embodiments, each coilis from 25 . . . 625 . . . 2500 . . . 62,500 . . . or 250,000 cm² inarea. The largest total series capacitance is needed for a conditionwhen all four coils have the same polarity. In some embodiments, thisseries capacitance is distributed equally among all four coils, balancedon each side of the switching relay as shown in FIG. 3. Distributingcapacitance this way keeps the contact voltage present at the switch toa minimum.

Otherwise, the high “Q” of the coils could result in excessively highvoltage, exceeding 10KV for some configurations, present at the switchesand interconnects.

Additional capacitance useful for maintaining a desired resonantfrequency as described above (e.g., adding capacitors in series toreduce the capacitance) is switched in by the polarity switching relayor a separate switch that may be energized when needed. In someembodiments, this capacitance is distributed among the polarityswitching relays to both minimize terminal voltage and minimize commonmode coupling by achieving best symmetry.

In some embodiments, each capacitance element is comprised of multiplecapacitors to minimize the voltage across each capacitor to ensure thevoltage capability of the capacitors is not exceeded and to minimizeheating due to losses that might otherwise cause the resonant frequencyto drift.

In some embodiments, a balun is incorporated as close as possible to theexciter coils (see Section D below and FIG. 3). The balun describedbelow accomplishes common mode rejection to reduce or eliminate electricfield generation and also provides an impedance transformation tooptimally match the coil assembly impedance to that of the transmissionline and power amplifier. In a some embodiments, the primary (amplifierside) of the balun has 8 turns and the secondary (coil side) has 4turns, thus providing a 4 to 1 change in impedance that nicely matches,for example, a 50-ohm generator output impedance to a 12-ohm coilimpedance at resonance. Other turns ratio may be employed for optimalimpedance transformation to other characteristic impedance transmissionlines and amplifiers.

FIG. 3 provides an exemplary embodiments of the coil system employed inthe exciter assembly. In this figure, a plurality of capacitors areidentified by number (e.g., C1, C5, C11, C40 etc.; pF (picofarads)) andtheir relative position to Coils A, B, C, and D (see, e.g., FIG. 4A). Abalun with a 7:4 turn ratio is shown (Balun transformer ratio matchesimpedance to 50 Ohms, employing 7:4 ratio, with 7 turns on the 50 ohmside and 4 turns on the coil side). The system may be configured oradjusted to optimize performance based on the manner in which the coilsare utilized. For example, as shown in the exemplary embodiment in FIG.3:

Field: Z-plane (++++) capacitors C9 and C10 are 25,600 pF (20,000 inparallel with 5,600 pF);

Field: X-plane (+−+−) capacitors C19 and C20 are 27,235 pF (used 27,000pF in parallel with series combination of (2) 470 pF capacitors);

Field: Y-plane (++−−) capacitors C29 and C30 are 6,050 pF (2,700parallel with 3,300 pF in parallel with series combination of (2) 100 pFcapacitors);

Common (all fields): capacitors C39 and C40 are 9,000 pF (parallelcombination of (3) 3,000 pF capacitor); and

C39 and C40 capacitors (value XY-fixed) are 9,000 pF (18,000 pF inseries with 18,000 pF; could be 9,220 pF; 8,200 in parallel with 820 pFor other combinations; total voltage is 660 Vrms).

Other specific values of capacitance may be utilized to provide thedesired resonance frequency or frequencies with different values ofinductance that may result from different coil constructions.

B. Addressing Exciter Field Strength Near Sensors

The exciter field strength used to power the tags, in general, is closeto the exciter in order to create a large volume in which a tag or tagscan be powered. This field is much larger than the field provided by thetag or tags or the emitters associated with a surgical tool (the tagsand emitters collectively and individually referred to herein as “thebeacons”). Also, since a single excitation assembly device is preferredto both provide excitation and sensing, the sensing components should bein close proximity to the exciter components. Therefore, the magneticfield sensors would normally sense a magnetic field at the exciterfrequency that is very large, on the order of 160 dB or more larger thanthe signals of interest (from the beacons).

This issue can be partially resolved by means of electronic filters.However, the rejection capabilities of these filters are limited, theyare expensive, and they are physically large. Filters may be active orpassive. However, active electronic filters have an inherent noise floorthat limits dynamic range and filtering effectiveness for this very highdynamic range situation so passive filters may be employed in someembodiments.

An alternative (or additive) solution takes advantage of the coil systemdescribed in Section A above. In such embodiments, one can reduce theexciter field pickup by the sensors by taking advantage of the vectornature of the magnetic field. In some embodiments, an exciter coil withan orientation generating only magnetic flux substantially perpendicularto the X-Y plane containing the sensing coils is selected. In someembodiments, ferrite-core coils, which are also highly directional innature, are then aligned to that plane, such that magnetic fluxorthogonal to the plane is not sensed. This produces rejection of theexciter field by more than 40 dB. In a preferred geometry, greater than70 dB of isolation has been achieved for all sensing coils in all threepolarity configurations described above. Both the height and tilt ofeach witness coil is adjusted to achieve the alignment needed to achievethis level of isolation for all three coil polarity conditions.Isolation is typically measured using a Vector Network Analyzer byconnecting the exciter coil to port 1 and a specific witness coil toport 2. The magnitude and phase of S₂₁ is then measured at the receivefrequency. In a preferred embodiment, the receive frequency chosen is130.2 KHz.

In such embodiments, the system therefore uses one magnetic fielddirection for excitation, and the two remaining directions (orthogonalto the excitation direction) for sensing. In other embodiments, one canuse two orthogonalities for excitation and one orthogonality forsensing. However, it may be preferable to use two orthogonalities forsensing to provide faster estimates of the beacon position(s).

C) Addressing Exciter/Beacon Coupling

In some embodiments, the exciter is a highly resonant coil. Because, insome embodiments, the beacon's frequency is close to the resonantfrequency of the exciter, a portion of the beacon's AC magnetic fieldaligned to the exciter coil orientation may induce current flow in theexciter and therefore produce a magnetic field in the exciter coilorientation at the beacon frequency. This effect distorts the originalfield from the beacon, making it more difficult to localize the beacon.In a clinically preferred geometry, this distortion masks the truelocation of the beacon such that navigation may become difficult orimpossible.

This coupling can be diminished by choosing a different beacon frequencyless close to the exciter resonance. However, because, in some preferredembodiments, the beacons utilize a single ferrite core RF coil for bothreception and transmission, the available bandwidth is limited.

Using the exciter configuration described in Sections A and B above,instead, since the sensing system comprised of sensing coils is orientedorthogonal to the exciter coil, the distorted field is not sensed. Inother words, distortion is limited to the magnetic field direction thatis substantially aligned to the exciter coil, which is orthogonal to thesensing system. The true location of the beacon is thus no longer maskedby the field distortion produced by the exciter current flow at thebeacon frequency so accurate navigation is achievable without artifact.

D) Addressing Electric Field Magnitude Produced by the System

The exciter and associated circuitry should be designed to minimize theelectric field magnitude produced by the system. If produced, electricfields can couple capacitively into the sensing system and degradesystem accuracy. Electric fields also interact with the patient and theenvironment much more significantly than magnetic fields.

In some embodiments, this challenge is addressed by incorporating abalun as close as possible to the exciter coils. The balun, which canalso act as an impedance transformer, minimizes electric field byeliminating asymmetric current flow with respect to ground. Another wayto think of this is that the balun eliminates common mode coupling. Insome embodiments, on the exciter side of the balun, the circuit designand layout should be as symmetric as possible to maintain balance.

In addition to reducing electric field effects, the transformer allowsoff the shelf 50-ohm coaxial transmission line to be used withoutmismatch. This scales transmission line voltage and current to optimallytransmit power to the exciter assembly with the best efficiency and thesmallest, most flexible, coaxial cable.

E) Identifying and Managing Locations of Multiple Beacons

In some embodiments, one or more beacons (e.g., tags, emittersassociated with one or more surgical devices, or other objects whoselocation, position, relative position, or other spatial informationdesired) are employed. In some embodiments, each different beacongenerates a unique frequency, spectrum of frequencies or otherwisedistinguishable signal. In some such embodiments, a hunting algorithm isemployed to identify the spatial information of one or more of thebeacons. In some embodiments, the optimal exciter polarity and powerlevel is identified for each beacon (e.g., accounting for any relativeorientation of beacon to the exciter) by cycling the exciter throughdifferent planes. Based on this information, an optimal exciter patternis calculated to maximize the quality of the procedure and accuracy ofinformation conveyed to a user (e.g., treating physician). In some suchembodiments, a first optimal pattern is utilized to provide spatialinformation about a first tag and a first portion of a procedure isconducted. Next, a second optimal pattern (which may be the same ordifferent) is utilized to provide spatial information about a second tagand a second portion of a procedure is conducted. Further cycles may beconducted for additional tags. Alternatively, the exciter pattern(polarity and power) may cycle between multiple, different optimalpatterns during a procedure to provide near real-time optimal spatialinformation of multiple beacons. In some such embodiments, rapidswitching of coil polarity in the emitter is employed to simultaneouslyor near-simultaneously power two or more beacons.

F) General Description of Exemplary System and Device Components

In some embodiments, the systems, devices, assemblies, and methods finduse in electromagnetic navigation systems that power a remote tag devicewith a sinusoidal magnetic field (see e.g., U.S. Pat. No. 9,730,764 andU.S. application Ser. Nos. 15/281,862 and 15/674,455, hereinincorporated by reference in their entireties). In some embodiments, thetag is wireless and ideally minimally sized. In some embodiments, whilepowered, the tag generates its own time varying magnetic field at one ormore sideband frequencies. The shape of the magnetic field isapproximately that of a magnetic dipole positioned at the tag. Bymonitoring the magnetic field at several positions with receivingantenna coils, also called sensing or witness coils or witness stations,the location of the tag is identified. In some embodiments, the systems,devices, assemblies, and methods further comprise an electrosurgicaltool. In some embodiments, the electrosurgical tool, or a componentattached to or in physical proximity to the tool, comprises two or morelocation emitters that also generate a magnetic field similar to amagnetic dipole. In some embodiments, the emitters are driven with twodifferent frequency signals that are also different from both theexciter frequency and the tag response frequencies. In certainembodiments, the location emitters are wired to a signal supply source.

In some embodiments, a single exciter assembly is employed (e.g., asshown in FIG. 4A) to generate signals that interact with the tag and thelocation emitters in the attachment component associated with theelectrosurgical tool. In some embodiments, the exciter assembly iscontained in a single thin assembly. In some embodiments, the assemblycomprising the exciter further comprises sensors (e.g., the receivingantenna/sensing/witness station coils). In some embodiments, the exciterassembly is configured to be deployed under a patient that is undergoinga medical procedure. An exemplary procedure configuration is shown inFIG. 1 with patient 90 positioned on a surface 95 (e.g., mattress oroperating table). The surface 95 is held by a surface frame 97. Thepatient 90 has a lesion (e.g., tumor) 110 and an implanted tag 100positioned near, on, or in the tumor. An exciter assembly 250 ispositioned beneath the patient, and beneath the surface (e.g., on thesurface frame 97), and generates an electromagnetic field (not shown) ina region around the patient encompassing the position of the tag 100 anda medical device 20 (e.g., surgical device) in the operating field abovethe patient.

FIG. 2 shows an exemplary electrocautery surgical device (e.g., BOVIE)that finds use in some embodiments of the invention. The device 20includes a tip 25 providing an operating surface for treatment oftissues, two embedded location emitters 70 allows the system to sensethe location and position of the device 20, and a display unit 40 thatprovides visual information to a user (e.g., surgeon) about the locationof a tag in the patient.

In some embodiments, the exciter assembly is configured to provideenhanced detection of remote objects (e.g., tags and surgical devices)under a number of different settings that would otherwise complicatelocation, position, and distance assessment, particularly real-timeassessment of such factors.

In some embodiments, the systems and methods comprise a plurality ofcomponents. In some embodiments, a first component comprises one or moretags (which may be used interchangeably with the term “marker”) whoselocation, position, distance, or other properties are to be assessed. Insome embodiments, the tags are configured to be positioned in a subjectat a surgical location or other clinically relevant location to mark atarget region within a body. In some embodiments, a second componentcomprises a remote activating device (e.g., exciter assembly) thatgenerates a magnetic field. In some embodiments, the second component islocated in a device positioned near (e.g., below) a subject containingthe one or more tags. In some embodiments, a third component comprises aplurality of witness stations configured to receive a signal generatedby the one or more tags upon being exposed to the magnetic fieldgenerated by the second component. In some embodiments, the second andthird components are physically contained in the same device (e.g., asshown in FIG. 4A). In some embodiments, a fourth component comprises amedical device location emitter. The fourth component can be integratedinto a medical device or attached or otherwise associated with anattachment component (e.g., sheath). The fourth component comprises oneor more location emitters (e.g., antennas that emit signals or othertypes of emitters) that generate signals via electrical wire feeds orupon exposure to the magnetic field generated by the second component,said signals detectable by the third component. In some embodiments, afifth component comprises a computing device comprising a processor thatreceives information from the witness stations of the third componentand generates information about the relative locations, distances, orother characteristics of the tags, the medical device, and the witnessstations. In some embodiments, the fifth component comprises a displaythat displays such generated information to a user of the system.

In some embodiments, the first component is a single tag. In someembodiments, it is two or more tags (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11,12, etc.). In some embodiments, where more than one tag is employed, thetags are of identical type while in other embodiments they are ofdifferent type.

In some embodiments, the tag comprises a ferrite-core coil antenna(e.g., resonant at 100-200 kHz) coupled to an integrated circuit (IC),which is powered by an AC magnetic field at resonance. In someembodiments, the core is contained in an enclosure (e.g., a cylindricalglass or plastic housing). In some embodiments, the exciter antenna(s)is/are driven by a conventional oscillator and power amplifier at alevel sufficient to power the tag(s). In some embodiments, the implantedtag amplitude-modulates (AM's) the continuous wave (CW) carrier powerfrom the exciter, thus emitting sidebands at frequencies defined by anumber programmed into the tag's counter. In some embodiments, thesesidebands, as well as the much stronger CW carrier, are ultimatelydetected by the third component.

In some embodiments, the tag comprises a self-resonant object (e.g., asmall ferrite core with a wound inductor). The wound inductor possessesinter-winding capacitance that in combination with the inductanceproduces a high frequency resonant circuit. In some embodiments, the tagcomprises a resonant object (e.g., the self-resonant object is equippedwith a chip capacitor to produce resonance at a prescribed frequency).In some embodiments, the tag comprises a resonant or self-resonantobject with a diode. A diode in combination with an LC circuit producesa sub-harmonic frequency when immersed in a magnetic field of sufficientstrength (imposed voltage exceeds the diode's band-gap potential). Insome embodiments, the tag comprises a resonant object or self-resonantobject with an active modulator (e.g., integrated circuit amplitudemodulates resonant circuit). In some embodiments, detection occurssimilar to a full duplex (FDX) radio frequency identification (RFID)except that the modulation pattern is a simple sub-harmonic rather thana coded binary pattern; in some embodiments, the detection occurs afterexcitation similar to a half-duplex (HDX) mode of operation.

In some embodiments, the tag is configured for single-use. In some suchembodiments, a tag can be disabled or deactivated (e.g., like an EAStag). This is particularly useful where multiple tags are used in aprocedure where individual tags are turned off to make detection ofother tags easier (e.g., to avoid or reduce interference betweenmultiple tags). In some embodiments, a burst of energy from an externaldevice is used to disable or deactivate a tag. In other embodiments, thetag has an internal control component that, upon receiving instructionfrom an external device, turns the tag on or off (e.g., the tag stops“talking” temporarily or permanently).

In some embodiments, the tag has an exterior length, width, and depth,wherein the length is 30 mm or less (e.g., 20 mm or less, . . . , 10 mmor less, . . . , 9 mm or less, . . . , 8 mm or less, . . . , 5 mm orless, . . . , 3 mm or less, . . . , etc.), the width is 5 mm or less(e.g., 4 mm or less, . . . , 3 mm or less, . . . , 2 mm or less, . . . ,1 mm or less, . . . 0.5 mm or less, . . . , etc.), and the depth is 5 mmor less (e.g., 4 mm or less, . . . , 3 mm or less, . . . , 2 mm or less,. . . , 1 mm or less, . . . 0.5 mm or less, . . . , etc.).

In some embodiments, the tag is contained in a housing. In someembodiments, no housing is employed. In some embodiments, the housingcomprises a biocompatible material. In some embodiments, the housingprovides a liquid and/or gas resistant barrier separating the signalsource from the exterior of the housing. In some embodiments, thehousing is small, permitting administration of the tag through a needle,cannula, endoscope, catheter, or other medical device. In some suchembodiments, the housing has an exterior length, width, and depth,wherein the length is 30 mm or less (e.g., 20 mm or less, . . . , 10 mmor less, . . . , 9 mm or less, . . . , 8 mm or less, . . . , 5 mm orless, . . . , 3 mm or less, . . . , etc.), the width is 5 mm or less(e.g., 4 mm or less, . . . , 3 mm or less, . . . , 2 mm or less, . . . ,1 mm or less, . . . 0.5 mm or less, . . . , etc.), and the depth is 5 mmor less (e.g., 4 mm or less, . . . , 3 mm or less, . . . , 2 mm or less,. . . , 1 mm or less, . . . 0.5 mm or less, . . . , etc.). The housingcan be of any desired shape. In some embodiments, the housing iscylindrical along the length axis. In some embodiments, the housing isshaped like a grain of rice (e.g., cylindrical with rounded ends). Insome embodiments, the housing is shaped like a pillar (e.g., cylindricalwith flat ends). In some embodiments, the housing is polygonal along thelength axis (e.g., triangular, square, rectangular, trapezoidal,pentagonal, etc., in cross-section). In some embodiments the housing hasstruts or other fasteners to keep the tag in place, avoiding migrationin tissue. These struts may deploy upon placement in tissue. In someembodiments the fastener may be a biocompatible material that bonds withsurrounding tissue.

In some embodiments, the housing is a single uniform componentsynthesized around the interior components of the tag. In otherembodiments, the housing is made of two or more separate segments thatare sealed together after introduction of the interior components of thetag. In some embodiments, the tag is completely or partially covered ina coating. In some embodiments, the coating comprises a biocompatiblematerial (e.g., parylene-C, etc.).

In some embodiments, the tag does not comprise any power source. Forexample, in some embodiments, the signal is generated from the signalsource in response to a magnetic field as the activation event (i.e.,electromagnetic induction).

In some embodiments, the tag comprises a radio-frequency identification(RFID) chip (e.g., in a housing). In some embodiments, the RFID chipcomprises a radio-frequency electromagnetic field coil that modulates anexternal magnetic field to transfer a coded identification number and/orother coded information when queried by a reader device. In someembodiments, the RFID chip collects energy from an EM field generated bythe second component (or other device) and then acts as a passivetransponder to emit microwaves or UHF radio waves. In some embodiments,the RFID chip is read-only. In other embodiments, it is read/write. Thetechnology is not limited by the nature of the information provided bythe RFID chip. In some embodiments, the information includes a serialnumber, lot or batch number, time information (e.g., production date;surgery date; etc.); patient-specific information (e.g., name, familyhistory, drugs taken, allergies, risk factors, procedure type, gender,age, etc.); procedure-specific information; etc. The technology is notlimited by the frequency used. In some embodiments, the RFID frequencyis in the 120-150 kHz band (e.g., 134 kHz), the 13.56 MHz band, the 433MHz band, the 865-868 MHz band, the 902-928 MHz band, the 2450-5800 MHzband, or the like. In some embodiments, the RFID chip is incorporatedwith browser-based software to increase its efficacy. In someembodiments, this software allows for different groups or specifichospital staff, nurses, and patients to see real-time data relevant tothe tag, procedure, or personnel. In some embodiments, real-time data isstored and archived to make use of historical reporting functionalityand to prove compliance with various industry regulations. In someembodiments, the RFID chip reports sensor data (e.g., temperature,movement, etc.). In some embodiments, the RFID chip contains or collectsinformation that is read at a later time (e.g., after surgery). In someembodiments, information is reviewed during surgery. For example, amessage may be provided to the surgeon (e.g., “the chip is just to theleft of the tumor”) to assist in guiding the surgeon (e.g., optimizingremoval of a tumor with the appropriate margins).

In some embodiments, the tag consists of or consists essentially of thesignal source and the housing or the signal source, the housing, and theRFID chip. In some embodiments, the tag (e.g., via the chip) emits anultrasound signal (e.g., gray scale, spectral, or color Doppler) suchthat the signal is detectable by an ultrasound probe or a hand-heldDoppler unit.

In some embodiments, a tag is heated during a procedure (e.g., viaexposure to an external energy source). In some such embodiments,heating may be used to assist in coagulation or precoagulation of tissueor to provide thermotherapy (see e.g., U.S. Pat. Publ. No. 2008/0213382,herein incorporated by reference in its entirety). Heating may also beused to improve the efficacy of radiation therapy.

In some embodiments, the second component provides a remote activatingdevice having one or more excitation coils (e.g., exciter assembly shownin FIG. 4A). In some embodiments, the excitation coils are provided in apatch or pad that is placed on the patient or on the operating table,although it can be positioned in any desired location within functionaldistance of the tags. In some embodiments, the remote activating deviceprovides an AC magnetic field originating from one or more exciterantennas. In some embodiments, where the system is used to locate breasttumors, the patch encircles the treated breast or is placed otherwisenear the breast.

Similar approaches may be used for other targeted areas of a body. Insome embodiments, a pad containing the excitation coil(s) are placedbeneath the patient. In such embodiments, a large coil or multiple coilsare employed. The excitation coil(s) may comprise or consist of severalturns of a flat conductor patterned on a dielectric substrate, or maycomprise or consist of magnet wire wound around a suitable mandrel; thecoil is powered by an external frequency source, and the magnetic fieldemanating from the coil penetrates the patient's body to excite the tag,whose emissions are detected by a detection component.

In some embodiments, the excitation coil or coils are contained in abelt that is placed around the subject or a portion of the subject. Insome embodiments, the external excitation coil may further be used forother aspects of the patient care, such as for radiotherapy or to act asa ground current return pad used in electrosurgery. In some embodiments,the remote activating device emits light (e.g., laser light). In someembodiments, the remote activating device is configured for single use(e.g., is disposable).

In some embodiments, the remote activating device employs an unmodulatedconstant frequency activation (i.e., the activation signal has constantamplitude and frequency). In some embodiments, the remote activatingdevice employs an unmodulated swept frequency (i.e., the activationsignal has constant amplitude and swept frequency between twoendpoints). Such devices find use with resonant-type tags such that adetectable change in the activation signal's amplitude occurs when thetransmitted frequency coincides with the tag's resonant frequency. Insome embodiments, the remote activating device employs a pulsedfrequency (i.e., the activation signal comprises brief excitation pulsesat a periodic frequency, which may be comprised of two closely-relatedfrequencies whose sum or difference is the response frequency of thetag). The pulsed activation produces a post-pulse sinusoidal decaysignal. A tag alters the characteristic of the decaying signal, eitherin amplitude or time.

In some embodiments, the remote activating device comprises a hand-heldcomponent. In some embodiments, the hand-held component is lightweightto allow a surgeon to hold and manipulate the component over the courseof a procedure (e.g., 5 kg or less, 4 kg or less, 3 kg or less, 2 kg orless, 1 kg or less, 0.5 kg or less, 0.25 kg or less, or any rangetherein between, e.g., 0.5 to 5 kg, 1 to 4 kg, etc.). In someembodiments, the hand-held component is shaped like a wand, having aproximal end that is held by the physician and a distal end that ispointed towards the treated subject or tissue harboring the tag. In someembodiments, the hand-held component is shaped like an otoscope, havinga distal end that terminates at an angle (e.g., right angle) from thebody of the component. In some embodiments, the remote activating devicecomprises an antenna that generates a magnetic field. In someembodiments, the remote activating device has only a single antenna(i.e., is monostatic). In some embodiments, the remote activating devicehas only two antennas (i.e., is bistatic).

In some embodiments, the magnetic field of the remote activating device(e.g., exciter assembly shown in FIG. 4A) is controlled by a processorrunning a computer program. In some embodiments, the remote activatingdevice comprises a display or user interface that allows the user tocontrol the remote activating device and/or monitor its functions whilein use. In some embodiments, the remote activating device provides avisual, audio, numerical, symbol (e.g., arrows), textual, or otheroutput that assists the user in locating the tag or identifying thedistance to or direction of the tag from the remote activating device.

In some embodiments, the plurality of witness coils of the thirdcomponent collectively provide several antennas at multiple definedlocations relative to the tags and configured to receive a signalgenerated by the one or more tags upon being exposed to the magneticfield generated by the second component.

In some embodiments, each witness coil feeds a receiver channel, whichis time-division multiplexed (TDM'd) to reduce the receiver complexity.Fixed witness stations of defined locations relative to the tag and eachother (e.g., arrayed along the patient) contain one or more (e.g., oneto three) witness coils arranged in a locally orthogonal manner to sensevarious components of the AC magnetic field from the tag. In someembodiments, one or more or all of these witness coils in the witnessstations is also TDM'd into a receiver channel, reducing complexity, aswell as cross-talk between antennas.

In some embodiments, witness coils comprise or consist of aferrite-loaded cylindrical coil antenna, tuned (e.g., with one or morecapacitors in parallel) for resonance at the frequency of an exciter(e.g., tag or emitter), (e.g., 100-200 kHz). Typical dimensions of awitness coils are 3-5 mm diameter and 8-12 mm length, although bothsmaller and larger dimensions may be employed.

In some embodiments, the witness stations are provided below the patient(e.g., in a pad, garment, or other device positioned below the patient).In some embodiments, the witness stations are integrated into a surgicaltable or imaging device in which a patient is placed during a medicalprocedure. In some embodiments, the witness stations are placed on thefloor, wall, or ceiling of the operating room or in a medical transportvehicle. In some embodiments, the witness stations are integrated intoor attached to a medical device used in the medical procedure.

In some embodiments, a fourth component provides a medical devicelocation emitter in an attachment component (see FIGS. 9-12) to allowthe system to determine the location, position, distance, or othercharacteristic of a medical device relative to the tag or tags. In someembodiments, the medical device location emitter or emitters areintegrated into a medical device or into an attachment component. Inother embodiments, they are attachable to a medical device. In some suchembodiments, the location emitters are provided in an attachmentcomponent (e.g., sleeve) that slips over a portion of a medical device.The location emitters may operate as and/or comprise the same materialsas the tags, but are positioned on or near a medical device rather thanwithin tissue. For example, in some embodiments, the emitters comprisecoils that are excited with both carrier and/or sidebands, enabling theemitters to emit signals as though it were a tag. In other embodiments,the location emitters are wired to a power and signal source.

In some embodiments, location of the location emitters is accomplishedgeometrically by measuring the quasi-simultaneous power detected fromthe emitters at a plurality of witness stations (e.g., four or morestations), and using the power differences to perform vector math thatdetermines the location of the emitter without ambiguity. This processis facilitated by a preliminary calibration using a known tag in a knownlocation prior to the procedure.

Vectors describing the location of the location emitters are used toprovide visualization guidance to the surgeon about the spatialrelationship of a medical device (e.g., particularly its tip) to animplanted tag, or (e.g., with computational guidance) to a lesionboundary. Use of multiple location emitters on an attachment componentattached to a medical device provides vectors to determine the device'sprincipal axis using the same vector math. Where a more complex medicaldevice, such as a robotic surgical system (e.g., da Vinci surgicalsystem) is employed, multiple location emitters located on multipledifferent locations of the device are employed to provide location,orientation, and other position information of multiple components(e.g., arms) of the device. In some embodiments, the location emittersare also used as detectors (e.g., provide witness stations on themedical device).

In some embodiments, a fifth component provides one or more computingsystems comprising one or more computer processors and appropriatesoftware to analyze, calculate, and display tag and emitter positioninformation (see, part 210 in FIG. 4A). In some embodiments, the displayprovides a graphical representation of the tag, patient, and/or medicaldevice on a monitor. In other embodiments, the display providesdirectional information for moving or positioning the medical device. Insome embodiments, the system automatically (e.g., robotically) controlsthe medical device or one or more functions thereof. In someembodiments, the display integrates tag and/or medical deviceinformation with previously obtained or concurrently obtained medicalimages of the patient or target tissue (e.g., CT, MRI, ultrasound, orother imaging modalities). For example, in some embodiments, an imageindicating a tag or tags is fused with an image of the subject's tissueor body region obtained from an imaging device. In some embodiments,information is analyzed in real-time. In some embodiments, informationis analyzed at one or more discrete time points.

In some embodiments, the fifth component provides command and controlfunctions for a user of the system. In some embodiments, the fifthcomponent has information stored thereon that helps guide theinformation displayed on the attachment component. For example, theinformation may include data on the type of medical device theattachment component is attached to, or what tip or cutting implement isbeing used with a particular medical device. In this regard, the preciselocation of the cutting tip of a medical device and its relation to thetag (e.g., distance to the tag) is communicated to the surgeon (e.g.,for very precise instructions on cutting tissue). Such information is,for example in some embodiments, manually entered into a control unit orattachment component by the user, or automatically found (e.g., by abarcode or other indicator) when a detection component is attached to aparticular medical device.

The system finds use with a wide variety of medical devices andprocedures. In some embodiments, the surgical device comprises anelectrical surgical device that is turned on and off by a user, whereina control unit that is part of the fifth component allows the remoteactivating device to generate the magnetic field when the electricalsurgical device is off, and prevents the remote activating device fromgenerating the magnetic field when the electrical surgical device is on(e.g., ensuring that the surgical device and detection system do notinterfere with one another). In other embodiments, the surgical devicecomprises a power cord, wherein an AC current clamp is attached to thepower cord, wherein the AC current clamp is electrically-linked orwirelessly linked to the control unit, wherein the AC current clampsenses when the electrical surgical device is on or off and reports thisto the control unit (e.g., such that the control unit can ensure thatthe magnetic field from the surgical device and from the remoteactivating device are not active at the same time).

In certain embodiments, the surgical device comprises an electrocauterydevice, a laser cutting device, a plasma cutting device, or a metalcutting device (e.g., a surgical device manufactured by BOVIE MEDICAL).Additional examples of medical devices that find use in embodiments ofthe system are found, for example, in the following U.S. Pat. Nos.9,144,453; 9,095,333; 9,060,765; 8,998,899; 8,979,834; 8,802,022;8,795,272; 8,795,265; 8,728,076; 8,696,663; 8,647,342; 8,628,524;8,409,190; 8,377,388; 8,226,640; 8,114,181; 8,100,897; 8,057,468;8,012,154; 7,993,335; 7,871,423; 7,632,270; 6,361,532; all of which areherein incorporated by reference in their entireties, and particularlywith respect to the hand-held medical devices disclosed therein.

In some embodiments, the attachment component has thereon, or attachedthereto, a display component for directing the surgeon to the tag ortags. In some embodiments, the display component provides: i) a spatialorientation indicator (e.g., visual, audible, etc.), and/or ii) adistance-to-tag indicator (e.g., visual, audible, etc.). In someembodiments, the display component comprises a first display forpresenting distance to tag information (e.g., visual, audible, lights,color, vibration, tactile, etc.), a second display for presentingvertical axis orientation, such as a preset preferred angle forapproaching a tag in a patient (e.g., a visual, audible, lights, colors,vibration, tactile, etc. display); and/or a third display for presentinghorizontal orientation (e.g., left to right information so the surgicaldevice can be centered when approaching the tag). In some embodiments,the display component comprises a plurality of displays (e.g., visual,audible, sensory, etc.) that allow the correct pitch and yaw axes to beemployed (to minimize non-target tissue damage), and/or further adisplay that provides distance to tag information. In certainembodiments, the medical device is moved around the patient's body priorto surgery to orient the emitters and the display component. In certainembodiments, a series of lights and/or sounds is provided on the displaycomponent that guides the surgeon (e.g., the surgeon attempts to keepthe lights in a center of an “X” series of lights, and/or to keep thevolume of warning sounds off or as low as possible).

The tag is not limited to placement within a particular body region,body part, organ, or tissue. For example, in some embodiments, the tagis placed in the cephalic, cervical, thoracic, abdominal, pelvic, upperextremities, or lower extremities region of the body. In someembodiments, the tag is placed within an organ system, such as theskeletal system, muscular system, cardiovascular system, digestivesystem, endocrine system, integumentary system, urinary system,lymphatic system, immune system, respiratory system, nervous system orreproductive system. In some embodiments, the tag is placed within anorgan. Such organs may include the heart, lungs, blood vessels,ligaments, tendons, salivary glands, esophagus, stomach, liver,gallbladder, pancreas, intestines, rectum, anus, hypothalamus, pituitarygland, pineal gland, thyroid, parathyroids, adrenal glands, skin, hair,fat, nails, kidneys, ureters, bladder, urethra, pharynx, larynx,bronchi, diaphragm, brain, spinal cord, peripheral nervous system,ovaries, fallopian tubes, uterus, vagina, mammary glands, testes, vasdeferens, seminal vesicles, and prostate. In some embodiments, the tagis placed within tissues, such as connective, muscle, nervous, andepithelial tissues. Such tissues may include cardiac muscle tissue,skeletal muscle tissue, smooth muscle tissue, loose connective tissue,dense connective tissue, reticular connective tissue, adipose tissue,cartilage, bone, blood, fibrous connective tissue, elastic connectivetissue, lymphoid connective tissue, areolar connective tissue, simplesquamous epithelium, simple cuboidal epithelium, simple columnarepithelium, stratified epithelium, pseudostratified epithelium, andtransitional epithelium.

In some embodiments, the tissue region where the tag is locatedcomprises a lesion. In some embodiments, the lesion is a tumor or atissue region identified as being at risk for forming a tumor. In someembodiments, the lesion is fibrotic tissue. In some embodiments, thelesion is an inflamed or infected region. In some embodiments, the tagis placed within a lumen to detect function or other process of theorgan or provide localizing information. For example, the tag could beswallowed, or placed into a hollow organ via endoscopy. In someembodiments, the tissue region is healthy tissue.

In some embodiments, the tag is placed within a solid tumor. Examples ofsolid tumors into which the tag may be placed include carcinomas,lymphomas, and sarcomas, including, but not limited to, aberrantbasal-cell carcinoma, acinar cell neoplasms, acinic cell carcinoma,adenocarcinoma, adenoid cystic carcinoma, adenoid/pseudoglandularsquamous cell carcinoma, adnexal neoplasms, adrenocortical adenoma,adrenocortical carcinoma, apudoma, basal cell carcinoma, basaloidsquamous cell carcinoma, carcinoid, cholangiocarcinoma, cicatricialbasal-cell carcinoma, clear cell adenocarcinoma, clear cellsquamous-cell carcinoma, combined small cell carcinoma, comedocarcinoma,complex epithelial carcinoma, cylindroma, cystadenocarcinoma,cystadenoma, cystic basal-cell carcinoma, cystic neoplasms, ductalcarcinoma, endometrioid tumor, epithelial neoplasms, extramammaryPaget's disease, familial adenomatous polyposis, fibroepithelioma ofPinkus, gastrinoma, glucagonoma, Grawitz tumor, hepatocellular adenoma,hepatocellular carcinoma, hidrocystoma, Hurthle cell, infiltrativebasal-cell carcinoma, insulinoma, intraepidermal squamous cellcarcinoma, invasive lobular carcinoma, inverted papilloma,keratoacanthoma, Klatskin tumor, Krukenberg tumor, large cellkeratinizing squamous cell carcinoma, large cell nonkeratinizingsquamous cell carcinoma, linitis plastica, liposarcoma, lobularcarcinoma, lymphoepithelial carcinoma, mammary ductal carcinoma,medullary carcinoma, medullary carcinoma of the breast, medullarythyroid cancer, micronodular basal-cell carcinoma, morpheaformbasal-cell carcinoma, morphoeic basal-cell carcinoma, mucinouscarcinoma, mucinous cystadenocarcinoma, mucinous cystadenoma,mucoepidermoid carcinoma, multiple endocrine neoplasia, neuroendocrinetumor, nodular basal-cell carcinoma, oncocytoma, osteosarcoma, ovarianserous cystadenoma, Paget's disease of the breast, pancreatic ductalcarcinoma, pancreatic serous cystadenoma, papillary carcinoma, papillaryhidradenoma, papillary serous cystadenocarcinoma, papillary squamouscell carcinoma, pigmented basal-cell carcinoma, polypoid basal-cellcarcinoma, pore-like basal-cell carcinoma, prolactinoma, pseudomyxomaperitonei, renal cell carcinoma, renal oncocytoma, rodent ulcer, serouscarcinoma, serous cystadenocarcinoma, signet ring cell carcinoma,signet-ring-cell squamous-cell carcinoma, skin appendage neoplasms,small cell carcinoma, small cell keratinizing squamous cell carcinoma,somatostatinoma, spindle cell squamous cell carcinoma, squamous cellcarcinoma, squamous cell lung carcinoma, squamous cell thyroidcarcinoma, superficial basal-cell carcinoma, superficial multicentricbasal-cell carcinoma, syringocystadenoma papilliferum, syringoma,thymoma, transitional cell carcinoma, verrucous carcinoma, verrucoussquamous cell carcinoma, VlPoma, and Warthin's tumor.

In some embodiments, placing the tag comprises the steps of inserting anintroduction device into the subject and introducing the tag through theintroduction device into the subject. In some embodiments, theintroduction device is a needle, cannula, or endoscope. In someembodiments, the tag is forced through the introduction device (e.g.,via physical force, pressure, or any other suitable technique) andreleased into the subject at the distal end of the introduction device.After the tag is placed, the introduction device is withdrawn, leavingthe tag at the desired location with the subject. In some embodiments,the introduction of the tag is guided by imaging technology.

In some embodiments, multiple tags are placed into the subject. The tagsmay be of identical type or may differ (e.g., differ in signal type).The tags may be placed in proximity to one another or at distantlocations. Multiple tags are used, in some embodiments, to triangulatethe location intended for medical intervention.

In some embodiments, the tags are further used as fiducials forradiotherapy (or other targeted therapy). The location of the tags isidentified with an external reader and used to place, for example, laserlight on the skin surface exactly where the chip is located. Thiseliminates the need to use X-ray, CT, or fluoroscopy to see thefiducials. This also decreases or eliminates the need to put skinmarkers (e.g., tattoos) on patients. This also helps in respiratorycompensation as the fiducial moves up and down with a tumor in the lungor abdomen. Therefore, one can conduct real-time radiation only when thetumor is in the correct position and decrease damage to the backgroundtissue (e.g., avoid burning a vertical stripe in the patient as thetumor moves up and down). The use as fiducials for director therapy(e.g., radiation therapy) also enhances triangulation as depthinformation (based on signal strength) assists in localization of thetumor to minimize collateral damage.

In some embodiments, provided herein are systems and methods employingone or more or all of: a) a tag (e.g., comprising an antenna; e.g., acoil antenna; e.g., a ferrite-core coil antenna; e.g., that resonates at100-200 kHz; e.g., coupled to an integrated circuit); b) a remoteactivation device that generates a magnetic field within a region of thetag; and c) a plurality of witness stations, each of the witnessstations comprising an antenna configured to detect informationgenerated by said tag or a change in a magnetic field generated by theremote activation device caused by said tag. In some embodiments, thetag emits sidebands at defined frequencies upon activation by a magneticfield and the witness stations detect such sidebands. In someembodiments, the tag emits the sidebands at frequencies defined by anumber programmed into a counter in the tag.

In some embodiments, the remote activating device comprises anexcitation coil that is, for example, powered by a generatorelectrically connected to the remote activating device. In someembodiments, the remote activating device comprises a pad configured tobe placed in proximity to (e.g., under, above, beside) a patient havingthe tag embedded in the patient. In some embodiments, the pad alsocontains the witness stations.

Any number of other tag designs may be employed. In some embodiments,the tag comprises or consists of a ferrous pellet or particle. When theferrous object is introduced within a magnetic field, the object createsan irregularity in the alternating magnetic field which is detectable bysense coils contained within witness stations, producing a phase andamplitude shift from null. The null is restored when the ferrous objectis physically equidistant to two sense coils.

In some embodiments, the tag comprises a self-resonant object (e.g., asmall ferrite core with a wound inductor). The wound inductor possessesinter-winding capacitance that in combination with the inductanceproduces a high frequency resonant circuit. Detection occurs, forexample, using the approach described above for the ferrous pellet or,for example, using a Grid Dip Oscillator (GDO). The GDO has a resonantcircuit that radiates an electromagnetic field. When proximal to theself-resonant object of the same frequency, power transfer from the GDOto the self-resonant object induces a detectable change in the GDOpower. In some embodiments, the tag comprises a resonant object (e.g.,self-resonant object is equipped with a chip capacitor to produceresonance at a prescribed frequency). In some embodiments, the tagcomprises a resonant or self-resonant object with a diode. A diode incombination with LC circuit produces a sub-harmonic frequency whenimmersed in a magnetic field of sufficient strength (imposed voltageexceeds the diode's band-gap potential). In some embodiments, the tagcomprises a resonant object or self-resonant object with an activemodulator (e.g., integrated circuit amplitude modulates resonantcircuit). Detection occurs similar to a full duplex (FDX) radiofrequency identification (RFID) except that the modulation pattern is asimple sub-harmonic rather than a coded binary pattern.

In some embodiments, each witness antenna comprises or consists of aferrite-loaded cylindrical coil antenna, tuned (e.g., with one or morecapacitors in parallel) for resonance at the frequency of an exciter(e.g., tag or emitter) (e.g., typically 100-200 kHz). Typical dimensionsof a witness antenna are 3-5 mm diameter and 8-12 mm length, althoughboth smaller and larger antenna may be employed. In some embodiments,witness station antenna has a ferrite core size of 0.25×1 inch andcontains 75-80 turns of a 10/46 (10 strands of #46) Litz wire whichprovides 0.157 mH (Q=53) (75 Turns).

In some embodiments, each witness coil is symmetrically wound about aferrite core and connected to the secondary of a small balun transformerthrough two series capacitances, one for each wire from the coil. Thetotal series capacitance is selected to resonate with the inductance ofthe coil, and the turns ratio of the balun transformer may be chosen tomatch the real impedance of the resonant coil/capacitor circuit to thetransmission line, typically 50 Ohms. The real impedance of the resonantcoil/capacitor circuit is typically 10 to 25 Ohms but may vary from justa couple Ohms to greater than 50 Ohms and may be adequately matched byappropriate choice of balun transformer primary and secondary turns. Inaddition to its role as impedance transformer, the balun minimizes anyelectric field generation/susceptibility from the witness coil assembly;alternately, it may be thought of as removing common mode effects.

In some embodiments, each witness station contains 1-3 witness antennasoriented orthogonally to each other and further arranged to have minimumcross-talk (i.e., interference with one another). The component housingthe witness stations further comprises one or more receiver channels forcollecting information obtained by the antennas of the witness stations.In some embodiments, the receiver comprises or consists of one or morechannels, each channel fed by one or more (via a multiplexing switch)witness antennas.

The component (e.g., attachment component) that contains the locationemitters may further comprise a display to assist the user in directingthe medical device to the tag during a surgical procedure. In some suchembodiments, a visual or audio display is provided on or associated withthe medical device that receives location information about the tag fromthe computer system. The display may be one or more directionalindicators such as LEDs, that indicate direction and/or distance to thetag. Color changes may be employed to indicate “on target” versus “offtarget” positions. In certain embodiments, the display comprises a firstdisplay for presenting distance to tag information (e.g., visual,audible, lights, color, vibration, tactile, etc.); a second display forpresenting vertical axis orientation, such as a preset preferred anglefor approaching a tag in a patient (e.g., a visual, audible, lights,colors, vibration, tactile, etc. display); and/or a third display forpresenting horizontal orientation (e.g., left to right information sothe surgical device can be centered when approaching the tag). In someembodiments, the display comprises a plurality of displays (e.g.,visual, audible, sensory, etc.) that allow the correct pitch and yawaxes to be employed (to minimize non-target tissue damage), and/orfurther a display that provides distance to tag information. In certainembodiments, a series of lights and/or sounds are provided on thedisplay that guide the surgeon (e.g., the surgeon attempts to keep thelights in a center of an “X” series of lights, and/or to keep the volumeof warning sounds off or as low as possible).

The technology is not limited by the mode of tag placement and a widevariety of placements techniques are contemplated including, but notlimited to, open surgery, laparoscopy, endoscopy, via endovascularcatheter, etc. The tags may be placed by any suitable device, including,but not limited to, syringes, endoscopes, bronchoscopes, extendedbronchoscopes, laparoscopes, thoracoscopes, etc. An exemplary protocolis provided below.

A patient previously identified as having a breast tumor is admitted toa medical facility. The patient is initially sent to radiology. Theradiologist examines prior imaging information identifying the targettumor. The subject is administered a local anesthetic, usually lidocaineor a derivative, using a needle introduced percutaneously. The subjectis positioned in an imaging device, generally either ultrasound,conventional mammography, or a stereotactic unit. The location of thetumor is determined. An introducer needle (usually 6-20 gauge) isinserted either into or just proximal to the tumor and a biopsy needleis placed through the introducer needle and a specimen is obtained usinga variety of methods (suction, mechanical cutting, freezing to fix theposition of the tissue followed by mechanical cutting). After thespecimen is obtained and sent for pathologic examination, a 6-20 gaugetag delivery needle is inserted into the coaxial introducer needle tothe tissue with the distal open end positioned at the lesion. A tag isinserted into the proximal end of the delivery needle and delivered byplunger through the opening at the distal end of the needle and into thetissue. Likewise, the tag could have been pre-positioned at the distalend of the delivery needle. Proper location of the tag is confirmed viaimaging. The delivery needle is withdrawn, leaving the tag in place inthe breast tissue.

This type of procedure can be performed in an analogous manner invirtually any body space, organ, or pathologic tissue with the intent oflocalizing that tissue or space for further diagnosis or treatment ofany kind. Areas of particular interest include but are not limited tothe following organs, and disease processes that take place within them:brain, skull, head and neck, thoracic cavity, lungs, heart, bloodvessels, gastrointestinal structures, liver, spleen, pancreas, kidneys,retroperitoneum, lymph nodes, pelvis, bladder, genitourinary system,uterus, ovaries, and nerves.

In some embodiments, during surgery, the patient is placed onto anoperating table with the surgical area exposed and sterilized. Thesurgeon is provided with the imaging information showing the location ofthe target tissue (e.g., tumor) and tag. An incision is made at thelocation of the entry point of the placement needle. The remoteactivating device is placed in proximity to the tissue to activate thetag. The detection component comprising the witness stations (e.g., asshown in FIG. 4A) detects a signal from the tag and allows the surgeonto guide the direction of the medical device toward the tumor. Once thetumor is localized, the surgeon removes the appropriate tissue and,optionally, removes the tag.

In some embodiments, the system finds use in surgery with the tagsplaced as fiducials on or in the body. The relative position of the tagsand any surgical instruments is located using the electromagnetic field.This information is communicated to a physician in real-time using avariety of methods including by not limited to visual (computer screens,direction and depth indicators using a variety of methods, hapticfeedback, audio feedback, holograms, etc.), and the position of theinstruments displayed on any medical images such as CT, MRI, or PETscans in 2D or 3D. This data finds use to guide the physician during aprocedure, or is used as a training method so that physicians canperform a virtual procedure. Such system may be integrated into orprovide alternative approaches to existing surgical systems, such as theSTEALTH system (Medtronic) for applications such as neurosurgeries.

In some embodiments, information about the location of the tag or tagsor the surgical paths or routes to the tags is conveyed to a surgeon orother user in a manner that comprises one or more augmented reality orvirtual reality components. For example, in some embodiments, a surgeonwears or accesses a virtual reality device (e.g., goggles, glasses,helmet, etc.) that shows a partial or complete virtual image of thepatient or surgical landscape. Tag position information collected andcalculated by the systems described herein are represented by one ormore visual components to the surgeons to assist in accurate targetingof the tag or tags. For example, the tissue containing the tag may berepresented with a virtual image of the tag location shown. Likewise, insome embodiments, a surgical pathway is visually presented, for example,as a colored line to be followed. In some embodiments employingaugmented reality features, a display, presents a graphical or videocapture of the patient representative of what the surgeon wouldvisualize if the monitor were not present and overlays one or moreaugmented features on the display. The graphical or video display datamay be captured by one or more cameras in the surgical field. Theaugmented features include, but are not limited to, a representation ofthe location of the tag in the target tissue, a projected surgical path,a target point to which the surgeon aligns the tip of the surgicaldevice, a simulated surgical margin zone to treat, arrows or otherlocation indicators that recommend movement if the optimal pathway isdeviated from, or the like.

An exemplary exciter assembly 250 is shown in FIGS. 4, 5, 6, and 7. Thisexciter assembly, as shown in FIG. 1, can be positioned under themattress of a patient lying on a surface, such as an operating table ormattress. The exemplary exciter assembly in these figures provides theexcitation signal, via four exciter coils 150, for the tag(s) in thepatient. The exemplary exciter assembly in FIG. 4A provides a pluralityof witness coil assemblies (aka witness station assembly) 161, each witha witness coil 160, in order to detect the signal from implanted tag(s)and the tags in the attachment component that is attached to thesurgical device. The exciter assembly is composed of a base substrate140 to which other components are generally attached or integrated into.The base substrate is composed of any suitable material, which may be,for example, polycarbonate or the like and is typically nonmagnetic andnon-electrically conducting. Not pictured in FIG. 4A is a top cover 230(see FIG. 8) that mates with the base substrate, enclosing all theinternal components therein. The top cover is composed of any suitablematerial, including Kevlar and/or other rigid materials, again typicallynonmagnetic and non-electrically conducting. Foam or other type ofpadding may be included on top of the top cover. Attached to the basesubstrate are four large exciter coils 150, which are labeled “Coil A,”“Coil B,” “Coil C,” and “Coil D,” in FIG. 4A. Each exciter coil 150 canbe wound around four exciter coil mounts 155. In certain embodiments,the exciter coils are not wound in any particular form and insteademploy wires that bond to themselves to create the coil shape. While notshown in FIG. 4A, in certain embodiments, coil covers (e.g., plasticcoil covers) are situated over each of the four exciter coils. Betweenthe four exciter coils, generally centrally located, is a large centralbalun circuit 180.

On the interior of exciter coils B, C, and D is a switch 190. The switch190 contains a component, such as a relay or multiple PIN diodes (e.g.,at least four PIN diodes), or filed effect transistor, that controls thedirectionality of the current (clockwise or counterclockwise) in therespective exciter coils. In the particular embodiment in FIG. 4A,excited Coil A does not have a switch 190 as the direction in this coilis not changed. The switch 190 is linked to difference capacitorsemployed to correctly match the different inductance resulting fromchanging the directionality of current flow. If a relay(s) (e.g., fourSPST, two SPDT type or one DPDT) is employed in the switch, it generallydirects an input to one of two outputs. If multiple PIN diodes areemployed (to create relay function) in the switch 190, this provides avery high impedance when “off” and low impedance when “on.” Each switch190 also is linked to one or more capacitors to modify the capacitancethat, along with the exciter coil inductor, forms the resonant circuit.This is necessary because the effective total series inductance of allexciter coils changes when the current flow direction is changed. Alsoon the interior of Coils A-D are a pair of capacitor assemblies 195,composed of a central capacitor 197, flanked by metal leads 199. Incertain embodiments, the metal leads 199, are affixed to ceramic heatspreaders, in order to dissipate heat that builds up during operation.

In operation, the exciter assembly in FIG. 4A is configured, in certainembodiments, to cycle between three configurations, called Configuration1 (shown in FIG. 5), Configuration 2 (shown in FIG. 6), andConfiguration 3 (shown in FIG. 7). In Configuration 1, as shown in FIG.5, the current from all four exciter coils is clockwise in order tosimulate an exciter coil generally aligned with its plane normal to theZ axis. In Configuration 2, as shown in FIG. 6, the current from Coil Aand Coil B is clockwise, while the current from Coil C and Coil D iscounterclockwise, in order to simulate an exciter coil generally alignedto the Y axis. In configuration 3, as shown in FIG. 7, the current fromCoil A and Coil C is clockwise, while the current from Coil B and Coil Dis counterclockwise, in order to simulate an exciter coil generallyaligned to the X axis. Although this is a preferred embodiment, othercombinations of coil polarities with other values of additional seriescapacitance may be advantageous for certain tag orientations. Forexample, the current in coil A, instead of being clockwise, could becounterclockwise, and then all of the other 3 coils (Coils B, C, and D)could have the current flow as shown in FIG. 5, 6, or 7, or the other 3coils (Coils B, C, and D) would have the opposite current flow as shownin FIGS. 5, 6, and 7. In other embodiments, the current arrangement isas shown in FIG. 6, except the current in Coil B is counterclockwise,and the current in Coil D is clockwise. Every different combination ofclockwise and counterclockwise for the Coils A-D is contemplated (i.e.,all sixteen combinations).

The exemplary exciter assembly 250 in FIG. 4A is also shown with twelvewitness station assemblies 161 (each with a witness coil 160). Thetwelve witness coils 160 alternate opposite orientation (along x and yaxes) to reduce crosstalk. In other embodiments, software may also oralternatively be used to reduce cross talk. In certain embodiments,rather than alternating orientation, all of the witness coils pointtoward the center, which would increase crosstalk, but may have theadvantage of shifting the location of inflection points in the witnesscoil signal pickups as a beacon is transitioned across the perimeter ofthe exciter assembly. It is generally preferably for the wires that feedinto the exciter coils not be in close proximity to any of the witnesscoils, to prevent reduction in isolation and noise pickup. In FIG. 4A,the wires from the center balun circuit to each of the four excitercoils are in a location away from the twelve witness coils 160. Also, asshown in FIG. 4A, the witness coils run down the left and right side ofthe exciter assembly, and do not run across the top or bottom of theexciter assembly. Adding witness stations across the top and/or bottomcan cause strong crosstalk to occur. Alternatively, softwareapplications can be used to reduce cross talk if witness coils areplaced in positions that induce crosstalk. The witness coils 160 areheld in place by a pair of witness coil brackets 165.

Next to each witness coil 160 is a printed circuit board 170. Eachprinted circuit board 170 contains capacitors and a small balun circuit.The capacitors, along with the witness coil, are employed to create aresonant circuit. The balun serves to eliminate common mode effects thatwould otherwise make the witness coil assembly susceptible to electricfield interaction. It also may serve as an impedance matching elementthat matches the real impedance of the coil/capacitor resonant circuitto the transmission line characteristic impedance, typically 50 Ohms, byoptimally selecting the number of primary and secondary turns.

The exciter assembly 250 in FIG. 4A is also shown with a pair ofself-test emitters 220. These self-test emitters 220 are present suchthat one can apply known signals and check the response on all witnesscoils. If a witness coils does not show the expected signal, itindicates a system problem, or could indicate the presence of aninterfering magnet or piece of metal which is distorting the field anddegrading overall localization accuracy. It is noted that anotherself-test that can be employed is to generate a signal on the excitercoils that is normally applied to one of the emitters on the attachmentcomponent (e.g., sheath on hand held surgical device). By measuring thesignal passed from the exciter to each witness coils, one can confirmthe level of isolation between them. In still another self-test, asignal may be applied to each witness coil individually and theremaining witness coils may be used to detect the signal. In otherembodiments, field witness coil crosstalk may also be measured this wayand used to calibrate the system.

FIG. 4A shows various wire connections between the various components ofthe exciter assembly. Each witness coil 160 is attached to a coaxialcable which is connected to the system electronics enclosure (labelled“controller,” 210) via the cable bundle 200. The exciter signal comesfrom the cable bundle 200 into the central balun circuit 180. Fromthere, wires carry the signal to the switches 190 and/or capacitorassemblies 195. The system electronics enclosure (controller 210)performs signal processing (e.g., filtering, mixing, amplification,digitization, and demodulation of multiple frequency ‘channels’) on thewitness coil signals. Generally, no A/C main power is applied to thewitness coils.

In regard to the capacitors employed in each capacitor assembly 195, andin the printed circuit boards 170, in general, the capacitors are chosento be COG/NPO type where the capacitance value does not change withtemperature, so that the resonant frequency of the exciter does notchange with temperature. The capacitors also provide a tuning networkwhich can selectively add capacitance in series to change the resonantfrequency, which helps reduce tolerances during manufacturing, as wellas makes it more tolerant of tuning changes due to temperature and otherfactors. In general, all the materials employed should have highdielectric strength and high stability over temperature to preventgeometric changes as the exciter assembly is used and the temperature israised.

An exemplary witness coil assembly (aka witness station assembly) 161 isshown in FIG. 4B Witness coil assembly 161 includes witness coil twowitness coil brackets 165, which are used to clamp an secure witnesscoil 160 against elastomer 162. The witness coil 160, as shown in FIGS.4B and 4C, is composed of a metal core (e.g., ferrite core) 166 andcoils 167 formed from wire. As shown in exemplary FIG. 4C, the metalcore 166 is composed of a central region 173 (under the wires in FIG.4C), with a wire-free proximal end 171 and a wire-free distal end 172.Only the ferrite core (using the proximal and distal ends that arewire-free) is clamped by bracket 165 and elastomer 162 (e.g., to providebest registration and eliminate the possibility of damaging the coilwindings 167 of witness coil 160). The height of each end of witnesscoil 160 may be adjusted up or down by adjustment screws 163 (present ineach witness coil bracket 165) while a restoring force is provided byelastomer 162. Elastomer thickness and durometer is chosen to providethe needed restoring force over the desired range of adjustment so thatthe adjustment screws will be easily adjusted yet hold the desiredsetting once the optimal position is achieved. Additionally, coilbrackets 165 each has a “V” or “U” shaped feature that allows them tosecure the proximal and distal ends of the metal core 166. This allows,for example, the brackets 165 to precisely register the witness coilcore (e.g., ferrite core) in the desired direction so it cannot rotateabout an axis perpendicular to the plane containing exciter coils. Thewitness coil assembly 161 also includes a printed circuit board 170(with capacitors and balun circuit) and a faraday shield 168. Thefaraday shield may be composed of conductive material, such as brass orcopper.

In certain embodiments, the exciter coil (e.g., as shown in FIG. 4A) isconnected to port 1 of a vector network analyzer or VNA. The witnesscoil output is generally connected to port 2 of the VNA and transmission(S21) is measured and displayed. This measurement is a directmeasurement of the signal present at port 2 resulting from excitationprovided to port 1 and is, therefore, a direct measurement of isolation.The lower S21 (more negative) the better. The more negative S21 thebetter. Typical isolation values (S21) achieved with the generallypreferred embodiment are −70 dB with usable ranges including −50 dB tomore than −100 dB (e.g., the noise floor of the VNA).

In general, to achieve the best isolation between exciter coil andwitness coil for the best accuracy over the largest navigation volume,it is generally important to position the witness coils orthogonal(e.g., precisely orthogonal) to the magnetic flux produced by theexciter coil. FIG. 4A shows such an orthogonal arrangement of the twelvewitness coils. Small offsets to height or tilt of the witness coil fromthis optimal position will generally result in signal coupling to thewitness coil from the exciter coil that undermines isolation.Accordingly, in certain embodiments, the screws (or other connectors) onthe witness coil brackets are employed to make fine adjustments.

FIG. 4C shows an exemplary witness coil 160, including how the coils 167are formed by wire being wound around the metal core in three stages: i)wind direction 1, where wire is wound around most of a first half of themetal core; ii) wind direction 2, where wire is wound over the top ofthe wire wound over the first half, as well as over most of the secondhalf of the metal core; and iii) wind direction 3, where wire is woundback over the wire on the second half. In certain embodiments, 80-140windings (e.g., 80 . . . 90 . . . 112 . . . 140) are on each half of themetal core (e.g., for total of 160-280 windings (e.g., 160 . . . 200 . .. 224 . . . 280). In certain embodiments, the wire is 32 AWG coppermagnet wire with a single layer polyester enamel and bond coat (e.g.,0.011 inches in diameter), and heat is used during wrapping to securewire wraps. In certain embodiments, the metal core is a ferrite corepart number #4077484611 from FAIR-RITE products corporation. In certainembodiments, the metal core (e.g., ferrite core) has a diameter of about10-15 mm (e.g., 10 . . . 12 . . . 14 . . . 15 mm), and is about 30-50 mmin length (e.g., 30 . . . 35 . . . 45 . . . 50 mm). In certainembodiments, the metal core has a diameter of about 12.7 mm and a lengthof about 41.5 mm.

The wire is also connected to the secondary of a small balun transformer(in the printed circuit board, part 170 in FIG. 4B) through two seriescapacitances (e.g., in the printed circuit board), one for each wirefrom the coil. In general, in certain embodiments, the total seriescapacitance is selected to resonate with the inductance of the coil inthe tag, and the turns ratio of the balun transformer may be chosen tomatch the real impedance of the resonant coil/capacitor circuit to thetransmission line (e.g., around 50 Ohms). In certain embodiments, thereal impedance of the resonant coil/capacitor circuit is typically 10 to25 Ohms, but may vary from just a couple Ohms to greater than 50 Ohmsand may be adequately matched by appropriate choice of balun transformerprimary and secondary turns. In addition to its role as impedancetransformer, the balun minimizes any electric fieldgeneration/susceptibility from the witness coil assembly; alternately,it may be thought of as removing common mode effects. To further reducethe electric field susceptibility, the use of a conductive faradayshield 168 over the balun and capacitors is employed. This faradayshield (e.g., Faraday cage) reduces the observed electric field tocomponents under the shield. Typically a Faraday shield is used toreduce the emission of electric fields of components under the shield,in this case it is also reducing the reception of electric fields.

FIG. 8 shows an emitter component 250 with the top cover 230 on. The topcover 230 may be composed of Kevlar or other suitably tough material.The exciter assembly 250 is shown with cable bundle 200 leading therein.

FIG. 9 shows an attachment component 10, with an angled distal end 300that the distal tip 25 of the medical device 20 is inserted through. Thedisplay component 40 is attached to an attachment component control unit310 via attachment component wire 60.

FIG. 10. Panel A shows the distal end 25 of a medical device 20 after itis initially inserted through the angled distal end 300 of attachmentcomponent 10. This view is prior to the attachment component wire 60being inserted into the cable management component 315. Panel B showsattachment component wire 60 prior to being attached to the cablemanagement component 315 of the display component housing 330. Panel Balso shows the housing tapered connection 340 that the proximal endtapered connection 350 of the attachment component 10 is inserted into.The cable management component 315 has two clips that align both theattachment component wire 60 and the medical device wire 50.

FIG. 11 shows an attachment component 10 attached to a display componenthousing 330. The attachment component 10 has a pair of location emitters70, which are linked to location emitter wires leads 72 which are insidetube 360. The location emitters 70 are powered by the wire leads 72 togenerate a signal which is detected by the witness coils. The attachmentcomponent also has an angled distal end 300 with a distal end opening305, which allows the tip of a medical or other device to be insertedtherethrough. The display component housing 330 has a cable managementcomponent 315, composed of a pair of clips for holding the attachmentcomponent wire and the medical device wire.

FIG. 12 shows an exemplary attachment component 10 attached to a displaycomponent housing 330 with a display component 40 located therein. Adisplay cover 370 is shown, which is used to secure the displaycomponent 40 inside the display component housing 330. Also shown is anadhesive strip 380 (e.g., a two sided strip with strong adhesive on bothsides), which is shaped and sized to fit inside the attachment componentand help secure a medical device to the attachment component.

FIG. 13. Panel A shows the proximal end tapered connection 350 of theattachment component 10, which is configured to push-fit into housingtapered connection 340 of the display component housing 330. Panel Bshows a close up of section A of Panel A, including cable managementtapered connection 317 that is part of cable management component 315and designed to be inserted into tapered connection hole 319 of displaycomponent housing 330. Cable management tapered connection 317 includesa flat part 318 to lock angular position.

FIG. 14 shows an exemplary system for localizing a tag that is implantedin a patient. The system is composed of an exciter assembly that emitssignals that activate the tags in the patient. A systems electronicsenclosure is shown as a mobile cart, which delivers signals to theexciter assembly and receives and processes signals from the tag(s) inthe patient and the location emitters in the attachment component.Guidance for a surgeon is displayed on the display component, as well ason a screen on the systems electronics enclosure.

We claim:
 1. A device comprising: a) a base substrate, b) first, second,third, and fourth exciter coils attached to said base substrate andconfigured to generate a magnetic field in three orthogonal directionsfor causing a tag to generate a signal, c) a plurality of switches thatcontrol the direction of current through said exciter coils, each of theplurality of switches is connected to one of said first, second, third,and fourth exciter coils; d) a balun circuit electrically linked to saidfirst, second, third, and fourth exciter coils, and e) a plurality ofwitness station assemblies.
 2. The device of claim 1, wherein each ofsaid witness station assemblies comprises: i) a witness coil, whereinsaid witness coil comprises: A) a metal core having a coil-free proximalend, a coil-free distal end, and a central region, and B) coil windingswound around said central region of said metal core, ii) a first witnesscoil bracket and a second witness coil bracket, and iii) a firstelastomeric part and a second elastomeric part, wherein said coil-freeproximal end of said metal core is secured between said first witnesscoil bracket and said first elastomeric part, and wherein said coil-freedistal end of said metal core is secured between said second witnesscoil bracket and said second elastomeric part.
 3. The device of claim 2,wherein said metal core comprises a ferrite metal core.
 4. The device ofclaim 2, wherein said first and second witness coil brackets eachcomprises at least one adjustment part.
 5. The device of claim 2,wherein said each witness station assembly further comprises anelectronics part electrically linked to said witness coil, wherein saidelectronics part comprises at least one capacitor and/or at least onebalun circuit.
 6. The device of claim 2, wherein said witness stationassembly further comprises a faraday shield.
 7. The device of claim 1,wherein each of the plurality of switches comprises a relay element, aPIN diode, or a field effect transistor.
 8. The device of claim 1,wherein each exciter coil comprises at least 50 turns and/or is composedof Litz wire.
 9. The device of claim 1, further comprising a pluralityof capacitors, wherein each switch is linked to at least two of saidcapacitors.
 10. The device of claim 1, wherein said plurality of witnessstation assemblies collectively comprises a plurality of witness coilsconfigured to detect said signal from said tag.
 11. The device of claim10, wherein said plurality of witness coils: i) are located on opposingsides of said base substrate, but not adjacent to said opposing sides,and/or ii) are each positioned to alternate opposite orientation along xand y axes with respect to other witness coils.
 12. The device of claim10, further comprising a plurality of printed circuit boards, whereineach of said plurality of witness coils is operably linked to one ofsaid plurality of circuit boards.
 13. The device of claim 12, whereineach circuit board comprises at least two capacitors and at least onebalun circuit.
 14. The device of claim 1, wherein the second excitercoil is electrically coupled to a first capacitance when current throughthe second exciter coil is a first polarity, and wherein the secondexciter coil is electrically coupled to a second capacitance, differentthan the first capacitance, when current through the second excitercoils is a second, opposite, polarity.
 15. The device of claim 1,wherein a resonant frequency of a series combination of first, second,third, and fourth excitor coils is adjusted with a capacitance.
 16. Thedevice of claim 1, wherein current in the first exciter coil travels ina clockwise direction when the magnetic field is generated in each ofthe three orthogonal directions.
 17. The device of claim 16, whereincurrent in the second exciter coil travels in the clockwise direction,current in the third exciter coil travels in the clockwise direction,and current in the fourth exciter coil travels in the clockwisedirection when the magnetic field is generated in one of the threeorthogonal directions.
 18. The device of claim 1, wherein each of theplurality of witness station assemblies is positioned orthogonal to oneof the three orthogonal magnetic fields.
 19. The device of claim 1,further including a plurality of capacitors providing a tuning networkto change a resonant frequency of the first, second, third, and fourthexciter coils.